textproduct: Albany

WHAT HAS CHANGED

For this afternoon, have increased temperatures slightly from the previous forecast based on current ASOS and NYS Mesonet obs. Still expecting temperatures to cool slightly this evening, but if warmer trend continues then spatial extent of wintry precip may need to be trimmed back this evening. Otherwise, while snow squall potential still exists for tomorrow evening, will note that this is looking like a more marginal setup.

KEY MESSAGES

- A wintry mix, including snow, sleet, and freezing rain, this evening into tomorrow morning may lead to slippery travel conditions, mainly for the high terrain areas.

- Gusty winds, lake effect snow, and isolated snow squalls are possible tomorrow afternoon and night, potentially leading to additional difficult driving conditions and/or some power outages.

- After a brief mid-week warm up, a clipper system brings a reinforcing shot of cold air to the region for the second half of the week.

DISCUSSION

KEY MESSAGE 1...As of 12:55 PM EST...After a dry start to the day, precipitation chances will increase from south to north through the afternoon and evening. GOES 16 WV imagery shows an upper low digging down across MN/WI, with a separate southern stream shortwave out ahead of the upper low over southern Mid- Atlantic states. A primary low associated with the northern stream feature is expected to slowly intensify as it tracks across the Great Lakes this evening into tomorrow, with a secondary low expected to develop near the NJ coast as cyclogenesis occurs within the next few hours. This feature can already be seen beginning to take shape, with current sfc analysis showing an inverted trough in this area. As the primary low tracks to our W/NW, it will result in low-level warm advection and isentropic lift, which along with a band of mid- level FGEN and CVA aloft will provide forcing for ascent for the precipitation this evening and tonight.

Temperatures at this time have warmed above the previous forecast, with almost the entire region above freezing. This is likely due to low-level cold air damming being offset by diurnal warming with the high clouds across our region remaining relatively thin so far this morning. That said, dew points are generally in the upper 20s to low 30s, so there will be some wet bulb cooling as precip begins. Additionally, we are still expecting temperatures to cool this evening with the loss of daytime heating, and the secondary low tracking off the coast will help to advect some cooler air down from the north. There remains uncertainty in the exact precip types and timing of transition given initially warm sfc temps and the fact that mid-level warm advection will be offset by diabatic cooling initially, with the 12z KALY sounding showing a significant mid- level dry layer. All that said, we did not make any changes to the existing winter weather advisory, as a wintry mix, including freezing rain, will remain possible for the high terrain areas and east-facing slopes this evening and tonight. Should the current warmer temperatures continue into this evening, we may have to trim back the spatial extent of the wintry mix and the advisory, however.

QPF amounts generally look on the light to moderate side, with a quarter to half inch of liquid. This will translate to a glaze to a couple tenths of flat ice for areas that see the most freezing rain, with up to a couple inches of snow and sleet for the ADKs. Precip will wind down tomorrow morning as a mid-level dry slot works into the region, but slippery travel conditions may still linger through the morning for areas that see wintry precip tonight. Finally, will mention that while widespread river flooding is not expected, there is currently a lot of ice on the Mohawk River, and river levels remain elevated due to runoff from snow melt yesterday into this morning. Ice appears to be moving/water flowing based on current webcams, which is a good sign. That said, should the ice become jammed up further downstream, then ice jam flooding would be possible. At this point, the probability of ice jam flooding still looks relatively low, but cannot totally be ruled out.

KEY MESSAGE 2... Tomorrow afternoon and night, the upper low will track to our north, near the NY/VT/NH border with Canada. The primary low gradually weakens, but the secondary coastal low begins to rapidly intensify once the upper low moves close enough to the Atlantic. At the same time, a 1034 mb sfc high will be located near Arkansans and western Tennessee, which will set up a tight pressure gradient across our area. 850 mb winds increase to 40-50 kt within a low-level cold advection regime that will help promote BL mixing. There are some questions as to just how much wind from aloft will be able to mix down to the surface with lake effect clouds around, the LLJ max moving overhead at night when there is a diurnal min in mixing, and lowering inversion heights. Therefore, confidence was not high enough to issue a wind advisory with this forecast package, but we will continue to mention the possibility for wind gusts up to 35-45 mph, with the strongest winds in the channeled NW flow favored areas of the Mohawk Valley, Capital District, and Berkshires. A few higher gusts to 50 mph will be possible if we can get enough mixing, with the most likely location in the Berkshires. Given that the ground will be thawed and in many areas and other areas may still have some ice on trees from tonight's freezing rain, some power outages will be possible due to the gusty winds. Gusts will be strongest tomorrow evening and night, with diminishing but still breezy winds Monday.

Additionally, the combination of strong NW winds, 850 temps briefly dropping as low as -14C, and moist cyclonic flow on the back side of the upper low will lead to lake effect and upslope enhanced snow showers. For the lake effect, favored areas will be the Mohawk Valley and northern Catskills with NW flow trajectories. With inversion heights reaching 750 mb tomorrow evening, there should be strong enough winds and enough lake-induced instability for the band to reach well into our CWA, but it should weaken overnight with warming 850 mb temps and lowering inversion heights. The upslope will be mainly along the NW facing slopes of the ADKs and southern Greens/Berkshires. Upslope will likely begin in the ADKs tomorrow mid to late afternoon, but may take a few more hours in the southern Greens until around 00z when Froude numbers drop below 2. For these areas, a general sub-advisory snowfall is expected with up to 1-3", but this could still result in some slippery driving conditions. Drier conditions are expected for most of the region Monday and Tuesday, but some lingering lake effect will be possible in the western ADKs Monday, with a clipper system Monday night potentially bringing a few additional light snow showers to this area.

As for the snow squall threat, if snow squalls develop the timing would likely be tomorrow late afternoon and evening. Latest 12z guidance still suggests that there is a low-end threat for snow squalls with the cold frontal passage, with the best chance in the western ADKs and western Mohawk Valley due to low-level moisture enhancement off of the Great Lakes. Main supporting feature for snow squall potential is the steep low-level lapse rates, although lack of a well-defined wind shift and/or strong low-level convergence along the cold front may limit the snow-squall threat, especially from the Hudson Valley eastwards due to less moisture and the loss of daytime heating as the front progresses eastwards.

KEY MESSAGE 3... Tuesday night into Wednesday, an upper trough with several embedded shortwaves will dig into the upper midwest and Great Lakes, with an associated sfc low tracking near or north of our region. Temperatures will likely rise to above normal levels ahead of this system on Wednesday, especially if the storm track is further north of our region. Precip chances will increase with/ahead of the system's cold front Wednesday and Wednesday evening, with rain or a rain/snow mix for valley area and a mix or all snow for the high terrain areas, especially north of I-90. Precipitation amounts generally look to remain on the light side at this time, but could increase slightly if the center of low pressure were to track further south, closer to upstate NY. Regardless, a much colder airmass with below normal temperatures then looks to move into the region behind the cold front by Thursday, and will linger through Friday. As this system tracks over and east of our region, the associated upper trough will amplify over the eastern third of the CONUS. Most sources of guidance have a wave of low pressure developing off the coast along the departing cold front Thursday. While some sources of guidance have this coastal low tracking close enough to bring some snow to the region, the more likely scenario at this time is for a storm track southeast of our region and out to sea due to the the positive tilt of the upper trough and the fact that the upper trough axis looks to set up further east than would be needed to a storm track closer to the coast. The cool pattern is expected to continue beyond the long term, with the CPC expecting below-normal temperatures for days 8-14, with near normal precip.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

Through 00z/Mon...A low pressure system and warm front will lift across the region tonight. Precipitation at all TAF sites will be mostly rain, though some sleet may mix in for a brief time at KGFL. Cigs and vsbys will gradually lower into the MVFR range by 02-03z/Sun then likely down to IFR by around 06z. Mainly IFR conditions with patchy drizzle is likely between 06-12z/Sun before a frontal boundary and wind shift improves conditions back to VFR for Sunday morning. VFR conditions are then expected into Sunday afternoon. Another disturbance could bring some snow showers or a rain/snow mix to some sites near the end of the TAF period so introduced PROB30 groups for this potential.

Periods of LLWS are expected until 06z/Sun at most sites as winds at 2000 feet increase to 30-40 kt. Surface winds will be variable at less than 10 kt or calm tonight then westerly on Sunday at around 10 kt with some gusts to around 20 kt.

Outlook...

Sunday Night: High Operational Impact. Very Windy With Gusts To 40 kts. Slight Chance of SHSN. Monday: Low Operational Impact. Breezy. NO SIG WX. Monday Night: No Operational Impact. NO SIG WX. Tuesday: No Operational Impact. NO SIG WX. Tuesday Night: Moderate Operational Impact. Chance of SHRA. Wednesday: Moderate Operational Impact. Chance of SHRA. Wednesday Night: Moderate Operational Impact. Chance of SHRA...SHSN. Thursday: Low Operational Impact. Slight Chance of SHSN.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...Winter Weather Advisory until 10 AM EST Sunday for NYZ032-033- 041-042-082-083. MA...Winter Weather Advisory until 10 AM EST Sunday for MAZ001-025. VT...Winter Weather Advisory until 10 AM EST Sunday for VTZ013-014.